Interpretive Summary: This paper deals with the determination of antioxidant capacity and a-amylase inhibitory activity of the essential oils from citronella grass and lemongrass. The chemical composition of the extracted essential oils was determined by GC-MS. The antioxidant capacity of the essential oils was determine by 2,2’-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging method, and the a-amylase inhibitory activity was evaluated by 3,5-dinitrosalicylic acid (DNSA) method. Both oils showed antioxidant and a-amylase inhibitory properties. IC50 values of the antioxidant capacity of both citronella grass and lemongrass oils were 0.46±0.012 and 4.73±0.15 µL/mL, respectively. While the a-amylase inhibitory activities, also expressed as IC50 = 6.59±0.20 and 6.97±0.12 µL/mL for the two oils were very similar. The results showed that both oils exhibited low antioxidant activity as compared to a-tocopherol standard. However, the a-amylase inhibitory activity was significantly higher as compared to acarbose drug currently used for controlling glucose levels in diabetic patients. Thus both these oils need to be further evaluated for antidiabetic potential. This project was written as a research grant proposal for a student to come and work at USDA for a short duration. However the grant was not approved and she did her work on composition data at Pakistan and phenolic profiles could not be included.

Technical Abstract:
The objective of the present study was to determine the antioxidant capacity of and in vitro a-amylase inhibitory activity of the essential oils extracted from citronella grass and lemongrass. The chemical composition of the extracted essential oils was determined by GC-MS. The antioxidant capacity of the essential oils was determine by 2,2’-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging method, and the a-amylase inhibitory activity was evaluated by 3,5-dinitrosalicylic acid (DNSA) method. Both oils showed antioxidant and a-amylase inhibitory properties. IC50 values of the antioxidant capacity of both citronella grass and lemongrass oils were 0.46±0.012 and 4.73±0.15 µL/mL, respectively. While the a-amylase inhibitory activities, also expressed as IC50 = 6.59±0.20 and 6.97±0.12 µL/mL for the two oils were very similar. The results showed that both oils exhibited low antioxidant activity as compared to a-tocopherol standard. However, the a-amylase inhibitory activity was significantly higher as compared to acarbose drug currently used for controlling glucose levels in diabetic patients. Thus both these oils need to be further evaluated for antidiabetic potential.